Electrical snap switch



Nov. 12, 1957 w. HERING 2,813,175

ELECTRICAL SNAP SWITCH Filed June 7, 1956 4 Sheets-Sheet l jzvrnforMurnau Halen/q Arr-a nui 1 Nov. 12, 1957 w. HERING 2,813,175

ELECTRICAL SNAP SWITCH Filed June 7, 1956 4 Sheets-Sheet 2 inzien/or ITTURNEY Nov. 12, 1957 w. HERING 2,813,175

ELECTRICAL SNAP SWITCH Filed June 7, 1956 4 Sheets-Sheet 3 .7nvenfarWALT/45A Hennig Nov. 12, 1957 w. HERING ELECTRICAL SNAP SWITCH 4Sheets-Sheet 4 Filed June 7, 1956 Javea/ar WALTHER. Humm/q l fb. r

. nent deformation coincident to overheating;

States My invention relates to an electrical snap switch of the typeincluding a contact-carrying spring leaf which is prestressed by alongitudinal compression stress and, therefore, tends when brought to aninstable central position to snap to one or the other of two endpositions.

Snap switches of this kind are particularly adapted for actuation bytemperature-responsive elements, such as bimetal strips, fortemperature-controlling purposes.

lt is an object of my invention to provide a snap switch of this type inwhich the flexibility of the spring leaf is localized to a certainsection or sections for the purpose of rendering the snapping actionmore abrupt and reliable.

Other objects of my invention are to so mount the contacts of the snapswitch as to effect their separation in transit by arresting one of thecontacts at an instant when both contacts while in engagement move withhigh speed; to provide means protecting the bimetal strip from permaandto provide means applicable where the snap switch serves forternperature-control purposes for increasing the sensitivity of the snapswitch to variations of temperature by imparting additional heat to thetemperature-responsive element.

`Further objects of my invention will appear from the detaileddescription of a number of embodiments following hereinafter withreference to the drawings. It is to be understood, however, that theterms and phrases used in such detailed description have been chosen forthe purpose of illustrating the invention rather than that ofrestricting or limiting the same, the features of novelty for whichpatent protection is sought being pointed out in the appended claims.

in tr e drawings,

Fig. l is an elevation, partly in section, of a snap switch used tocontrol the temperature of an electric iron, the snap switch being of atype in which the contact carried thereby and the point of engagement ofthe actuating force with the spring leaf is located in a stilfenedcentral section thereof,

Fig. 2 is a plan View of the snap the adjusting knob being omitted,

Fig. 3 is a more or less diagrammatic elevation of a modified snapswitch of a type in which the point of engagement of the actuating forceonly is located in the stiffened central section of the spring leaf,whereas the contact carried by the spring leaf is spaced from suchstiffened section, the neutral position of the spring being shown infull lines, whereas its end positions are shown by dotted lines,

Fig. 4 is a more or less diagrammatic elevation of .a snap switchdiffering from that shown in Fig. 3 by the provision of abutments forthe spring leaf,

Fig. 5 illustrates the same switch shown in Fig. 4 with the springassuming another position,

Fig. 6 is an illustration similar to that of Figs. 3, 4 and 5 of a snapswitch in which the actuating member is rigidly connected with thespring leaf,

Fig. 7 illustrates a snap switch similar to that shown 1n switch shownin Fig. 1,

atent Oiiice 2,813,175 Patented Nov. 12, 1957 Fig. 4 in which theactuating member engages the spring at a point spaced from the stitfenedsection of the spring,

Fig. 8 is an elevation of a snap switch similar to that shown in Fig. 3in which the actuating member is formed by a laterally projecting arm,

Fig. 9 is a snap switch similar to that shown in Fig. 6 and differingtherefrom in that the stiifened section has the same thickness as themore resilient end sections of the spring leaf,

Fig. 10 illustrates a snap switch similar to that shown in Figs. 6 and 7in which the contact carried by the support is mounted in a resilientand adjustable manner.

Fig. 11 shows a snap switch including a spring leaf having two spacedstiffened sections,

Fig. 12 shows a snap switch in which the actuating member is formed by abimetal strip stiifening a central section of the spring leaf,

Fig. 13 is an elevation of a snap switch in which one of the ends of thespring leaf only is rigidly secured to the support, the other end beingsecured to a bimetal strip,

Fig. 14 illustrates the switch shown in Fig. 13 with the element thereofassuming another position,

Fig. 15 is an elevation of a switch in which one of the contacts iscarried by the actuating member and acts on the spring to move samethrough the instable central position,

Fig. 16 is a cross section through a switch similar to that shown in anyone of the Figs. 3, 4 and 5 in which the actuating member comprises apair of relatively movable elements connected by a spring,

Fig. 17 is a cross section through a switch similar to that of Fig. 16in which a bimetal strip acting on the actuating member is connected tothe support by means of a spring,

Fig. 18 is a plan View of an elongated switch spring leaf in which themore resilient sections are rendered more exible by lateral recesses,

Fig. 19 is a plan view of a switch spring leaf in which the moreresilient sections are each rendered more flexible by a plurality ofrecesses,

Fig. 20 is an elevation of a snap switch in which the central section ofthe switch spring leaf is stiflened by lateral flanges,

Fig. 2l is a bottom View of the spring leaf shown in Fig. 20, crosssections of the spring leaf being inserted in such figure,

Fig. 22 is an elevation of a Switch similar to that of Fig. 1 andserving the same purpose as the same,

Fig. 23 is a plan View of the switch shown in Fig. 22, and

Fig. 24 is an end view of the switch shown in Fig. 22 viewed from theleft.

On the bottom plate of an electric iron a column composed of blocks 31,32 and 33 interconnected by suitable screws is mounted. Holders 34 and35 carrying terminal connecting screws are interposed and clampedbetween such blocks. A spring leaf 36 is interposed and clamped betweenthe block 33 and the holder 35 and extends laterally from the column andcarries a substantially horizontally disposed elongated frame 37 of asuitable insulating material, such as ceramic material, for resilientupward and downward movement. The blocks 31, 32 and 33 likewise consistof a suitable insulating material. An elongated switch spring leaf 38 iscarried by the frame 37, the ends of the spring leaf being rigidlyclamped to the end members of the frame, for instance by rivets 39 and40, the spring leaf 38 extending across the opening of the frame. Atransverse bridge member 41 is carried by the side members of the framebeing so disposed as to span the opening of the frame and the springleaf thereabove. The bridge member is provided with a tapped bore accommodating an adjusting screw 42 constituting an abutment limiting thedeflection of the spring leaf 38.

When the spring leaf 38 is disassembled from the frame 37 and is inrelaxed condition, the distance of the holes serving to accommodate therivets 39 and 40 is somewhat larger than the distance between the rivets39 and 4t). Therefore, when the spring leaf 33 is fixed to thesupporting frame 37 it will be pre-stressed by a longitudinalcompression stress producing a tendency of the spring 38 to snap from aninstable central position to one or the other of two end positions. Forenabling the spring to be so pre-stressed its end section disposed atthe left with reference to Fig. l is formed with corrugations. For apurpose which will be described later its central section spaced fromthe ends of the spring leaf is stiffened so as to be practicallynon-resilient. Hence, the spring leaf includes two end sections ofgreater resiliency and a central section therebetween of lesserresiliency. When the spring snaps to its upper end position itsstiffened section 43 engages the adjustable stop 4Z. When the springleaf snaps to its lower position, however, a contact 44 secured to thestiffened section of the spring leaf at the bottom thereof engages acountercontact 45 which is mounted on the support 37, preferably byresilient means. in the embodiment of the present invention illustratedin Fig. l such resilient means is formed by a spring leaf 46 extendingbeneath the frame 37 and having its left end secured thereto by suitablemeans not shown, whereas the right end of the spring leaf 46 is providedwith a tapped bore engaged by a threaded stem of the contact 45, suchthreaded stem carrying a counternut 27 for the purpose of adjustment.The contact 45 is located within the opening of the frame 37 beneath thecontact 44 carried by the stilfened section of the spring 38. A exibleconductor 47 connects the spring leaf 46 with the terminal holder 34.The other terminal holder 35 is electrically connected with the contact44 through the intermediary of the spring leaf 36 and the spring leaf38.

Moreover, the frame 37 is provided with a bore accommodating anactuating member in form of a pin 48 which may engage the right hand endof the stiifened section 43 of the snap spring leaf from below and iscontrolled in dependence on the temperature by a temperature-detectingelement. As long as the temperature is below a predetermined limit thespring leaf 38 assumes a position beneath its instable central positionand, therefore, urges its contact 44 against the contact 45 whereby thecircuit for heating the electric iron is established. When thetemperature of the bottom plate 36 of the electric iron exceeds acertain limit, however, the temperature-detecting element will lift thestiffened section 43 at the right hand end thereof. During the initialphases of this lifting operation the longitudinal compression stress setup in the spring leaf 38 and more particularly in the corrugationsthereof holds the contact 44 in engagement with the contact 45 while thestiffened section 43 of the leaf is slightly tilted by the ascending pin48. This tilting motion continues until the spring lleaf passes throughits neutral condition and abruptly snaps upwardly away from the Contact45 and the pin 48 and engages the stop screw 4Z, whereby the contacts 44and 45 are separated interrupting the circuit heating the electric iron.

In the embodiment of the invention illustrated in Figs. l and 2 thetemperature-responsive element is a bimetal strip 49' mounted in arecess 5t? of the bottom plate 30 of the electric iron, such bimetalstrip having its left end clamped to the bottom plate 3@ by means of theinsulating block 31. On its right end the bimetal strip carries a platel which projects beyond the bimetal strip and has an insulating lining52 on which the actuating pin 48 is supported. When the temperature ofthe electric iron is low the parts assume the position illustrated inFig. l. As the temperature rises the bimetal strip 49 is exed upwardlyso that its top face will become convex 4 whereby the plate 51 will liftthe actuating pin 48. A layer 53 of insulating material serves toinsulate the spring leaf 46 from the bimetal strip 49.

For the adjustment of the temperature limit at which the snapping actionof the switch is effected, the level of the insulating frame 37 may beadjusted. This frame has two lateral projections 54 resting on a pair ofparallel arms 55 of a tiltable frame 56 mounted for adjustment about ahorizontal axis on the insulating block 33 whereby the pair of arms 55may be rocked up and down. The frame 56 has a recess 57 through which avertical threaded spindle 5S extends, such spindle being rotatablymounted in a supporting plate 59 mounted on the insulating block 33. Anut 60 is engaged by the threaded spindle 5t; and slots 6i are providedin the side faces of such nut. These slots are engaged by the opposededges of the recess 57 of the frame 56. By rotation of the spindle withthe aid of a knob 62 ,the nut 6i? may be moved upwardly or downwardly.Such movement causes the nut to rock the frame 56 and the arms 55thereof. The spring 36 tends to maintain the projections 54 of the frame37 in engagement with the arms 55. When the bimetal 49 is considerablyflexed, however, it may lift the frame 37 causing the projections 54thereof to be lifted from the arms 55, whereby the bimetal strip isprotected from a permanent deformation which, in event of a rigidconnection of the frame 37 to the arms 55, would be liable to occur whenthe knob 62 is adjusted to a low temperature at a time when the bottomplate Sii has a high temperature.

For protecting the switch from dust the top of the frame 37 may beclosed by a cover 63 indicated by dotted lines.

The spring leaf 46 carrying the contact 45 may be formed as a heatingresistance adapted to heat the bimetal strip 49. As a result, thetemperature difference existing between the temperature causing theelectrical circuit to be closed and the temperature causing theelectrical circuit to be interrupted will be reduced. When the partsassume the position shown in Fig. l the heating circuit is closed. Whenthe temperature rises above the cut-off limit the spring leaf 33 snapsupwardly and separates the contacts 44 and 45 and moves to engagementwith the stop 42. Now the temperature of the iron drops. ln the initialphases of the drop of temperature the left end of the stiffened section43 of the spring leaf remains in contact with the stop screw 42, whereasthe right end of the stiffened section 43 drops gradually until thespring leaf 38 passes through its neutral condition and snaps downwardlyto thereby close contacts 44 and 45 again. Ordinarily the turn-ontemperature is somewhat lower than the cut-off temperature. Thedifference between the two temperature limits is reduced by the abovedescribed heating effect exerted by the spring leaf 46 upon the bimetalstrip 49.

The stiffening of the spring leaf 38 throughout its central section 43may be effected in various ways, for instance by increasing thethickness of the spring leaf within this central section by acoextensive metal strip soldered to the spring leaf 38.

The snap switch described adapted to abruptly separate and engage thecontacts 44 and 45 to thereby avoid sparking between the contacts andthe consequent wear and radio disturbance, excels by its safe operation,its longevity and its ability to operate at comparatively hightemperatures which may amount to 240 C. for instance, provided that aheat-resistant spring metal is chosen for the spring leaf 38. Also thesnap switch excels by the low mass of its movable elements whereby theimpact, wear and noise incidental to its operation are reduced to aminimum. Since the spring leaf 38 is mounted to its support 37 withoutthe use of any pivots, no friction and consequent wear will occurbetween the spring leaf and the support.

The novel snap switch described including an elongated spring leafinstable in a central position because of a suitable bias and thustending to snap into one or'the other of its end positions, such springleaf being rigidly clamped to its support without any pivotal connectiontherebetween, may be modified in numerous ways.

Thus, Fig. 3 illustrates an embodiment in which the ends of a springleaf 66 are rigidly clamped in a support 65. A central section 67 of thespring leaf is stitfened again. The non-stitfened end section at theleft is corrugated. The spring leaf is pre-stressed by a longitudinalcompression bias and, therefore, tends to snap from its instable centralposition B illustrated in full lines upwardly or downwardly into thepositions A or C shown in dotted lines. The spring leaf 66 carries anelectrical contact 68 in spaced relationship to the support 65, suchcontact being adapted to engage a stationary countercontact 69 carriedby the support. A suitable actuating member not shown may exert anactuating force k1 or k2 upon the spring leaf at a point spaced fromboth the support 65 and the contact 68. If it is desired to move thespring leaf from the position A to the position C, the actuating forcek1 must be rendered effective to displace the spring leaf. Suchdisplacement will cause the spring leaf to snap into the position C. Bythen applying the actuating force k2 the spring leaf may be restored tothe position B causing it to snap back to the position A.

The snap switch shown in Fig. 3 differs from that shown in Fig. l by thedisposition of the contact 68 on the non-stifened, highly resilientcorrugated end section of the spring leaf, whereas in Fig. l the contactis mounted on the non-resilient central section of the spring leaf.Moreover, in the snap switch of Fig. 3 the contact is mounted on the topof the spring leaf, whereas in Fig. l it is mounted at the bottomthereof. A further difference resides in that in Fig. 3 the spring leafis in a stable condition in both end positions A and C tending to remaintherein owing to its bias, whereas the spring leaf 38 in Fig. l is in astable condition in its lower position only. When it assumes its upperposition in engagement with the stop 42 then it requires pressureexerted by the actuating pin 48 in order to maintain the spring leaf insuch upper position. When the spring leaf is relieved from the pressureexerted by the actuating pin 48 it commences its downward motion. Thevarious phases of this motion are illustrated in Figs. 4 and 5.

In Figs. 4 and 5 the support 37 is indicated diagram- 'matically. Theopposite ends of the spring leaf 38 are firmly clamped to the support37, the central section 43 of the spring leaf being stitfened. Theactuating pin 48 exerts the force k3. The stop 42 limits the snappingmotion of the spring leaf in upward direction and the contact 45, whichfor sake of simplicity is shown as being stationary, limits the snappingmotion in downward direction. The lowermost position of the spring leafis indicated in full lines in Fig. 4.

When the force k3 exerted by the actuating member 48 increases it willex the right hand end section of the spring leaf upwardly moving thecentral stifened section 43 to the inclined position E indicated bydotted lines. In this position the spring leaf is in its instableconditon. It will be noted that in this first phase of the operationwhen the spring leaf moves from its lowermost position to the positionE, the contacts 44 and 45 in Fig. l will remain closed. As soon as thespring leaf is lifted beyond the position E it will snap abruptly intoits upperrnost position F, the stiffened central section 43 being tiltedunder the effect of the bending stress set up in the spring leaf at 70causing the left end of the stiffened 'section to swing upwardly. In theposition F the spring leaf is kept by the force k3, as illustrated inFig. 5 in full lines, provided that the force k3 is sufficientlypowerful to overcome the effect of the bending stress set up in thespring leaf A38 at 71. As soon as the force k3 .decreases so as tobeovercome by such bending stress,

the stilfened central portion of the spring leaf will rst move into theinclined position indicated in Fig. 5 by dotted lines, such inclinedposition resulting in a substantially stable condition of the springleaf. Only upon a further reduction of the actuating force k3 will thesnapping action occur whereby the spring leaf will snap into theposition H. In this snap switch an actuating force acting in a negativedirection, as indicated in Fig. 3 by the arrow k2, is not required.Hence, it will appear that the spring leaf because of the effect of itsstiffened central section 43 is capable of assuming two positions inwhich it is in a substantially stable condition, such positions beingthe positions indicated in Fig. 4 at E and the position indicated inFig. 5 at G.

In Fig. 6 I have indicated a snap switch differing from that shown inFig. 3 and that shown in Figs. 4 and 5 by the fact that the actuatingpin 72 does not engage the stitfened section 43 but rather engages thenon-stiffened right hand end section being rigidly xed thereto, forinstance by a rivet, any pivotal connection being avoided. This offersthe advantage that no wear may occur between the spring leaf and theactuating member. The snapping operation is the same as that explainedhereinabove with reference to Figs. 4 and 5.

In the embodiment illustrated in Fig. 7 the point of engagement of theactuating member with the spring leaf is located in the non-stiffened,highly resilient right hand end section of the spring leaf just as inthe embodiment of Fig. 6. The actuating pin 73, however, acts on thespring leaf without being rigidly connected thereto, the operation beingsimilar to that described hereinabove with reference to Figs. l and 2.

In the embodiment of the snap switch illustrated in Fig. 8 the actuatingpin has been replaced by an arm 74 which is riveted to the spring leafand projects laterally out of the supporting frame 75. The right handend of this arm may be mounted for pivotal movement about a stationarypoint. The actuating forces k5 or k6 will act on this arm, such forcessetting up bending stresses in the highly resilient right hand endsection of the spring leaf 76, such bending stresses initiating thesnapping action. The snapping operation occurs in the manner explainedwith reference to Fig. 3.

This embodiment may be modied by securing the arm 74 to the stiffenedsection 77 of the spring leaf rather than to the resilient section 76.This modification is particularly well adapted for such cases where theactuation is to be effected by a torsional force. This torsional forceis caused to act on the arm 74 about the pivotal axis (not shown)thereof.

In Fig. 9 I have illustrated a snap switch differing from `theembodiments described hereinabove by the fact that the stilfened sectionhas the same thickness as the nonstiffened, highly resilient endsections of the spring leaf. In this embodiment the stiffening of thecentral sectionl is effected by an increase of its width. Alternatively,the highly resilient end sections rof the spring leaf may have the samewidth as the stiifened central section, but may be weakened by lateralrecesses increasing the flexibility of the end section.

That is illustrated in Fig. 19 showing a spring leaf having a centralsection 78 of the same thickness as the highly resilient end sectionswhich have their `ends rigidly clamped in the support 79. Theflexibility of the end sections may be also increased by lateralrecesses where the central section is stiffened in the manner explainedhereinabove with reference to Figs. l and 2.

That is illustrated vin Fig. 18 showing a spring leaf 'having a centralsection reinforced by imposition of a plate 81 rigidly secured to thespring leaf, whereas the end sections 82 are provided with lateralrecesses 83 increasing their flexibility.

The actuating pin 84 (Fig. 9) may be rigidly connected to the springleaf, for instance by being riveted thereto, and may engage either thestiiened central section 78 ora more flexible section. Y YTheembodim'ent illustrated in Fig. 10 differs from'those describedhereinabove with reference to Figs. 3 and 9 by the fact that thecountercontact ES is not rigidly mounted on the support 86 but isadjustably and resiliently mounted thereon. For this purpose, thecontact 85 is mounted on the end .of a spring leaf 87, the other end ofsuch spring leaf being riveted to the supporting frame 86. The springleaf 87 engages a setting screw 88 mounted in a tapped bore ofthesupporting frame 86 and serving to adjust the bias of the spring leafS7. Otherwise this embodiment may be identical with that explained withreference to Figs. 4 and 5.v The adjustability of the bias of the springleaf 87 aids in assuring that the snapping operation will be effectedina rapid and reliable manner.

In the em-bodiment illustrated in Fig. ll the spring leaf is stiffenedthroughout a pair of spaced sections 89 and 90. The section intermediatethese stiffened 'sections is highly flexible being corrugated as shownat 91. The points where the contact is mounted on the spring leaf andWhere the latter is engaged by the acutating member may be chosen -inaccordance with `any one of the examples described hereinabove and isnot illustrated in Fig. ll.

Y 'In the embodiment of the snap switch illustrated -in Fig. 12 thecentral section of the lspring leaf 92 is stiifened by 'bimetal strip 93which is united rigidly with the spring leaf, for instance by soldering.As long as this bimetal stripv 93 assumes a straight shape the springleaf will remain in its lower position indicated in full lines. When the'bimetal strip due to a change of temperature is bent upwardly it willset up a bending stress in the spring leaf causing sameto move throughits neutral condition and to snap int-o the position indicated by dottedlines. By this snapping effect the switch contacts will be engaged. IInthis embodiment, too, the two limit positions of the spring leaf couldbe predetermined by stationary and preferably adjustable stops. Thebimetal strip 93 thus performs both functions, that of stiffening thecentral section `of `the spring Ileaf 92 and that of the actuatingmember.

IIn Fig. 13 I have illustrated a snap switch in which the switch springleaf 94 has but one of its ends rigidly secured to the supporting frame.A central section of the spring leaf is stiifened by a plate 96 bondedto the spring. The right hand end of the spring leaf 94 is riveted tothe free end of a lbimetal strip 97 by a -rivet 101, the other end ofthe bimetal strip being rigidly `clamped in the support 975 preferablyin engagement with the end of the switch spring leaf 94. The spring leaf94 is pre-stressed by a longitudinal compression bias. When the bimetalstrip 97 assumesa certain `temperature it will maintain theV parts inthe position illustrated in full lines in Fig. 13. iIn this position thestiffened section 96 of the spring leaf engages ya rigid stop 98 mountedon the 4support 95, whereas the contact 99 mounted on the stidenedsection of the spring leaf is disengaged from the countercontact 100mounted on the bimetal strip 97. Upon a chan-ge of the temperaturecausing the bimetal strip to bend in a manner whereby its right hand endwill be lifted, the parts will first move t-o a non-stable position inwhich the contacts V100 .and 99 are still separated. Upon passagethrough this non-stable position, the parts will snap into the positionVindicated in Fig. 14 in which the stiffened central section of thespring leaf is .slightly spaced from the stop 98, Whereas the rivetconnecting the spring leaf with the bi- 'metal strip 97 engages theframe. In this position the con- ,tactsy 99 and 100 engage each other.The stop 98 may be likewise formed by a contact. The snapping operati-onis ,promoted by the bending stress produced -by the rivet joint 101.

A heating coil may be mounted on the bimetal strip 97 and maybe suppliedwith current under the control by the contacts 99, 100. In this event,the snap switch acts as a "blinker switch which automatically andperiodically closes and interrupts the electrical circuit, forV instancefor the purpose of controlling blinker lights.

=In the snap. switch illustrated in Fig. l5 the-point ofren-V gagementof the actuating force coincides with the point where the contact islocated on the spring leaf, the actu; ating force being inserted on thereinforced section 102 of the spring leaf 104 by a pair of spacedabutrnents 105 and 106 mounted on the endl ofV an actuating member, forinstance on the end of a bimetal strip 107'hav-ing its other end rigidlysecured to the support 103. In this embodiment, both ends of the switchspring leaf 104 :are firmly. clamped to the support 103. Whereas theabutment 106 is Idirectly attached to the end of the bimetal strip 107,the abutment 105 is carried lby a rigid arm 108 of the bimetal strip.The `abutment 106 may be formed as an electrical contact whichcooperates with a countercontact 1,09 mounted on the stiffened section102 of the spring leaf.

The spring leaf 104 is pre-stressed by a longitudinal compression biasand, for this purpose, is provided with suitable corrugations. This biasproduces a tendency of the spring leaf to snap from an instable centralposition to one or the other of two end positions. In Fig. 15 I haveillustrated a condition in which the spring leaf tends to movedownwardly and, therefore, engages the abutment 106 with a certainforce. Upon a change of the temperature in a manner causing the bimetalstrip 107 to rise, the abutment 106 will move the spring leaf 104through its non-stable position and beyond the same causing the snappingoperation to occur whereby the spring leaf moves abruptly upwardlycausing its stiifened central section to engage the abutment 105. Ifdesired, the movement on the abutment 106 may be limited by a rigid stopmounted on the frame 103. In this embodiment, too, the bimetal strip 107may be provided with a heating coil energized by an electric currentcontrolled by the contacts 106 and 109. When the bimetal strip 107 isheated it will rise and move the abutments 105 and 106 upwardly. Thenthe snap switch shown in Fig. l5 will act as a periodical intermittentinterrupter.

In Fig. 16 I have illustrated a cross section through a snap switch inwhich the actuating pin is riveted to the switch spring leaf. Thetransverse section through the switch shown in Fig. 16 may be thatindicated by the line 16-16 of Fig. 6 or by the line 16-16 of Fig. 9.The actuating pin 84 is riveted to the spring leaf 110. In certain casesit may be desirable in spite of the rigid connection between theactuating pin and the spring leaf to permit the temperature-responsiveelement to move independently of the spring leaf. Tothis end, theactuating pin 84 is connected with a U-shaped spring leaf 111 to whichan actuating pin is attached, the pin 85 being disposed coaxially to thepin 84 and being rigidly secured to the temperature-responsive element112 which may be constituted by a bimetal strip.

A similar effect may be attained in the switch illustrated in Fig. 17showing a switch spring leaf 113 which is rigidly connected by theactuating pin 114 with the one end of a bimetal strip 115, the other endof such bimetal strip, however, being not rigidly secured to the support116 but being secured thereto through the intermediary of an auxiliaryspring leaf 117. This auxiliary spring leaf will protect the bimetalstrip Vfrom excessive stresses resulting in a permanent deformationwhich, in the absence of the auxiliary spring, could occur when thebimetal strip tends to bend beyond the limits permitted by the switchspring leaf 113.

In Fig. 20 I have illustrated a snap switch differing from thatillustrated in Fig. 3 essentially by the fact that the stiiening of thecentral section of the spring leaf 118 is effected in another manner.Whereas in the embodiment shown in Fig. 3 a strip or plate is bonded tothe central section of the spring leaf to be reinforced, no such stripis provided in the embodiment shown in Fig. 20, the switch spring leaf118 being simply provided with lateral downwardly bent anges 119 so thatthe stiened central section has a channel-shaped cross section asindicated in Fig. 2l. Otherwise the snap switch shown in Figs. 20 and 2lis similar to that shown in Fig. 3.y Thus, the spring leaf 113 has bothof its opposite ends firmly clamped in the supporting frame 120 in amanner prestressing the spring leaf by a longitudinal compression bias.The contact 122 is mounted on the left highly resilient end section ofthe spring leaf and cooperates with a stationary contact 121 mounted onthe supporting frame 120, such stationary contact acting at the sametime as a stop limiting the upward movement of the spring leaf. Theactuating member 123 is rigidly secured to the reinforced section of thespring leaf by a rivet or a screw 124.

In Figs. 22, 23 and 24 1 have shown a switch which serves the samepurpose as that illustrated in Figs. 1 and 2 differing therefrom mainlyby its simplified and more compact structure. A base plate 110' issecured to the outwardly extending llanges of an inverted U-shaped framemember 111 provided in its upper horizontal portion with a boreaccommodating a vertical shaft 112', the lower end face of such shaftresting on the base plate 110' and being provided with a stud 113'journalled in a bore of the base plate 110'. A horizontal pin 114'extends past the shaft 112' through the Vertical sections of the framemember 111' and is mounted therein. Spaced vertical ears 116 of asupporting member 117' are pivotally mounted on the pin 114'. Thesupporting member 117' is connected by a helical traction spring 118with the upper portion of the frame member 111. The spring 11S' keeps adownwardly projecting arm 119' of the supporting member 117' inengagement with a cam 120' secured to the shaft 112. The latter has aknob (not shown) permitting to turn the cam and to thereby adjust theangular position of the supporting member 117. The supporting member117' has a horizontal arm 121' having its upper and lower face lined bymica sheets 122 and 123'. A terminal sheet metal plate 124 is imposed onthe mica sheet 122 and projects laterally, as shown in Fig. 23, forconnection thereto of an electrical conductor 125. A supporting member126 is secured to the plate 124 and extends substantially parallel tothe arm 121'. The downwardly turned end of the member 126 carries anadjusting screw 127. A switch spring leaf 128 has one end rmly clampedbetween the plate 124 and the frame member 126 and has its other endbent upwardly and rearwardly and firmly fixed to the top of the framemember 126, as indicated at 130. It will be noted that the bent sectionof the spring leaf 128 is slightly spaced from the downwardly bent endof the supporting member 126 and the head of the adjusting screw 127. Aresilient sheet metal member 131 which is likewise iixed to thesupporting member 126 extends between the head of the adjusting screw127 and the bent portion of the spring leaf 128 bearing against thelatter at 132. The adjusting screw 127 is tightened thereby causing thesheet metal member 131 to prestress the spring leaf 128 by alongitudinal compression stress producing a tendency of the spring leafto snap from an instable central position to one or the other of two endpositions. When the parts assume the position shown in Fig. 22 thespring leaf 128 assumes a position lower than its neutral position and,therefore, tends to move downwardly thus keeping a contact 133 securedto it between its ends in engagement with a countercontact 134 disposedbeneath the Contact 133 and carried by a spring leaf 135 which underliesthe mica sheet 123 and is clamped thereagainst by another mica sheet136.

An electrical heating element 137 formed by a resilient strip of asuitable conductive material has one end connected to the spring leaf135 beneath the contact 134 to be in conductive connection therewith andhas its other end electrically connected to a terminal metal sheet 138that is clamped between the mica sheet 10 136 and another mica sheet139. A washer 140 underlies the mica sheet 139 and a rivet extendsthrough the superimposed elements 126, 128, 124', 122', 121', 123', 135,136, 138, 139 and 140 thus holding the same firmly together in steppedcondition. Two spaced sections of the spring leaf 128 are stitfened bysheet metal plates mounted thereon. One such section indicated at 141 isdisposed between the terminal sheet 124' and the contact 133 and spacedtherefrom. The section 141 is stitened by a sheet metal strip foldedaround the spring leaf 128 and soldered thereto. The other section ofthe spring leaf 128 that is stiffened is indicated at 142. It overliesthe contact 133 being conductively connected therewith and extends closeto the point 132 and has a hole for the passage therethrough of a stopscrew 149 which will be described later. It is likewise reinforced by asheet metal strip folded around the spring leaf 128 and solderedthereto. This reinforcing sheet metal strip forms a depending resilientbent tongue 143 adapted to be engaged by an actuating member 144consisting of a block of insulating material fixed to the end of ahorizontal arm 145, which, in its turn, is fixed by a rivet 146 to thefree end of a bimetal strip 147. The other end of the bimetal stripunderlies the base plate and is clamped by the same against the baseplate 30 (Fig. 1) of the electric iron and is thus firmly held incontact therewith. When the temperature of the base plate 30 of theelectric iron rises, the bimetal strip 147 bends upwardly lifting theactuating member 144 and causing it to engage the tongue 143 to therebylift the spring leaf 128 towards and through its neutral position. As aresult, the spring leaf 128 snaps upwardly into Contact with a stopscrew 148 carried by the supporting arm 126. During the initial phase ofthe upward motion of contact 133 the bias spring leaf will lift thecontact 134 keeping the same in engagement with the Contact 133. Whenboth contacts have reached a comparatively high velocity and shortlybefore the spring leaf 128 will arrive in contact with the stop 148, theend of the spring leaf 135 will be arrested by engagement with the lowerend of the adjustable screw 149 carried by the supporting arm 126. Atthe instant when this arrest occurs contact 133 continues its upwardmotion at high speed thus ensuring a particularly quick separation ofthe contacts 133 and 134 whereby any sparking will be avoided. The endof the spring leaf 13S is lined with a mica plate 150 for the purpose ofelectrical insulation of the stop screw 149.

The temperature at which the snapping action occurs depends on thealtitude of the tongue 143 above the base plate 30 of the electric ironand may be adjusted within wide limits by rotation of the shaft 112'.

The stops 148 and 149 are so adjusted that the contacts 133 and 134 willbe separated a distance suflicient to ensure the interruption of any arcthat may form. Moreover, this adjustment and that of the adjusting screw127 must be effected in such a manner as to ensure that the spring 128when engaging the stop 148 will descend as soon as the tongue 143 isrelieved from pressure by the actuating member 144. As a result, thecontacts 133 and 134 will re-engage as soon as the temperature dropsbeneath a certain limit. If desired, however, the adjustment of thestops 14S and 149 and the adjustment of the screw 127 may be so eectedthat the spring leaf 128 will remain in its upper position in engagementwith the stop 148 even after the tongue 143 is relieved from pressure bythe actuating member 144. With this adjustment the novel snap switchillustrated in Figs. 22 to 24 may be used for the purpose of cutting olfthe current from an electrical apparatus should the latter be heated toan excessive temperature. With that adjustment it will be necessary fora re-engagement of the contacts 133 and 134 to depress the spring leaf128 manually, for instance by a temporary lowering of contact 148 orotherwise.

The electric circuit controlled by the snap switch extends through theconductor 125, the terminal sheet 124';

11 theaswitch, spring-f leaf 128, the contact 133, thecontactlLtlie-heating element 137, the terminalsheet 138, and thewire 1.51,; Y

The resilient tongiiefllV limits the reactionary force actingon, theactuatorV 144 thereby preventingv permanent, deformation of the, bimetalstrip 147 should the same-be heated beyondthe cut-off temperature.

The stiffeningy of thev sections 141 and 142 of the springL leaf 128maybe effected in the manner described hereinabove with reference toFigs. 18, 19, 2O and 2l, thatl is to say by an increase of the width orby ateral tianges; rather than by'a separate and additional metal sheete While the invention has been described in connection with :njnnmber ofpreferred embodiments thereof, it will be understoodthatit is capableofV further modification, and, this application is intended to cover anyvariations, uses,4 or; adaptations ofthe invention following, ingeneralthe.principles of the invention and including such departuresfrom the present disclosure as come within lrnowrn or; customarypractice in the art to which the inyentionrpertains, and as fallwithinthe scope of the invention orV the-limitsof the appended claims.

What l claim is: Y -Y *1., A snap switch comprising a support, a switchspring leaf having. lat least one central section of greater width andzconsequent stiffness than the adjoining end sections ofjjsaid spring.leaf, means for rigidly securing said end sectionof*4 saidv spring leafto saidsupport and for prestressing said spring leaf by a longitudinalcompression stresslproducing` a tendency of said spring leaf to snapfrom,Y an` instable central position to one or the other of two endpositions, a rst contact carried by said spring leaf in spacedrelationship to saidV support, a second contact` mounted for engagementby said first contact in one ofA said, end positions, abimetal element,means for mounting one. end of said bimetal element in fixed condition,an actuating member mounted on the other end of said bimetali elementfor movement relative to said support in response to changes oftemperature, said actuating member being so disposed relative toV saidspring leaf as to move same through said instable central position whenthe temperature` increases beyond a predetermined limit.

2A. A snap switch comprising a support, an elongated switchy springleaf, means for rigidly securing the opposite ends of said spring leafto said support and for prestressing said spring leaf by a longitudinalcompression stress. producing a tendency of said spring leaf to snapfrom an instable central position to one or the other of two endpositions, a first contact carried by said spring leaf between its ends,a second contact cooperatively coordinated to said first contact,resilient means movably supporting said second contact and tending tomaintain same in engagement with said first contact, an actuating membermounted for relative movement with respect to said support for acting onsaid spring leaf to cause movement of same away from said second contactthrough said instable central position, a iirst stop carried byfsaidsupport for arresting said second contact prior to the termination ofsaid movement, and. a second stop coordinated to said spring leaf tolimit said movement, saidv stops being so disposed relative to eachother as to permit said first contact to travel in the course of saidmovement through a longer distance than said second Contact.

3. A snap switch as claimed in claim 2 in which said second stop iscarried by said support.

4.. A snap switch as claimed in claim 2 further cornprising meansy foradjusting said support towards and away from said actuating member.

5. A snap switch as claimed in claim 2 further comprising` a frame,means for movably mounting said support thereon, an adjusting camrotatably mounted in said frame for engagement with said support, aspring connected; to Said. slipped t0, hold; Same, in engagement withsaid cam, and a bimetal strip havingr one endV fixed to said fratrieAandthe other end carrying said actuating, member. Y

Y k6. A snap switch comprising aV frame, a support pivoted thereto foradjustment about an axis, an adjusting cam rotatably mounted in suchframe in engagement with said support, said support having an armextending substantially radially with respect to said axis, an elongatedswitch spring leaf substantially coextei'isive with said arm having itsends fixed thereto, the end of said spring leaf remote from said axisbeing bent over the end of said4 arm inspaced relationship thereto,adjustable means secured to the end of said arm and engaging the bend ofsaid leaf to set up a longitudinal compression stress therein producinga tendency of said spring leaf to snap from an instable central positionto one or the other of two end positions, a first contact carried bysaid spring leaf between its ends, a second contact cooperatively colordinated to said first contact, resilient means` fixed to said supportand movably supporting said second contact and tending to maintain samein engagement with said first contact, an actuating member mounted forrelative movement with respect to said support for acting on said springleaf to cause movement of same away from said second contact throughsaid instable central position, a first stop carried by said support forarresting said second contact prior to the termination of said movement,and a second stop coordinated to said spring leaf tovlimit saidmovement, said stops being so disposed relative to each other as topermit said first contact to travel in the course of said movementthrough a longer distance than said second Contact.

7. A snap switch comprising a support, an elongated switch spring leafhaving stiened sections spaced from each other and from the ends of saidspring leaf, means for rigidly securing said ends of said spring leaf tosaid support and for pre-stressing said spring leaf by a longitudinalcompression stress producing a tendency of said spring leaf to snap froman instable position to one or the other of two end positions, a firstcontact carried by one of said stiffened sections of said spring leaf, asecond contact mounted for engagement by said first contact in one ofsaid end positions, and an actuating member movable relative to saidsupport for acting on said stiffened sections of said spring leaf tomove same through said instable central position.

S. A snap switch comprising a support, a switch spring leaf having atleast one section of less iiexibility than the adjoining sections ofsaid spring leaf, means for rigid/ly securing said adjoining sections ofsaid spring leaf to said support and for pre-stressing said spring leafby a longitudinal compression stress producing a tendency of saidVspring leaf to snap from an instable central posi- Ytion to one or theother of two end positions, a first con.- tact carried by said springieaf in spaced relationship to said support, a second contact mountedfor engagement by said first contact in one of said end positions, abimetal element, means for mounting one end of said bimetal element infixed condition, an actuating member mounted on the other end of saidbimetal element for movement relative to said support in response tochanges of temperature, said actuating member being so disposed relativeto said spring leaf as to engage said section of less exibility tothereby move said leaf through said instable central position when thetemperature increases beyond a predetermined limit, and an electricalheating element electrically disposed in series with at least one ofsaid contacts and mounted adjacent to said bimetal element.

9. A snapl switch comprising a support, a switch spring leaf having atleast one central section of greater width than the adjoiningendsectionsof said spring leafmeans for rigidly securing said end sections to saidsupport and for pre-stressing saidV spring leaf by a longitudinalcornpression'L stress producing .a tendency Of saidY spring leaf to snapfrom an instable central position to one or the other of two endpositions, a first Contact carried by said spring leaf in spacedrelationship to said support, a second contact mounted for engagement bysaid first contact in one of said end positions, a bimetal element,means for mounting one end of said bimetal element in ixed condition, anactuating member mounted on the other end of said bimetal element formovement relative to said support in response to changes of temperature,said actuating member being so disposed relative to said spring leaf asto engage said central section to thereby move said spring leaf throughsaid instable central position when the temperature increases beyond apredetermined limit.

10. A snap switch comprising a support, a switch spring leaf having atleast one central section having lateral anges reducing the flexibilityof said central section compared with that of the adjoining sections ofsaid spring leaf, means for rigidly securing said adjoining section ofsaid spring leaf to said support and for pre-stressing said spring leafby a longitudinal compression stress producing a tendency of said springleaf to snap from an instable central position to one or the other oftwo end positions, a first contact carried by said spring leaf in spacedrelationship to said support, a second contact mounted for engagement bysaid first contact in one of said end positions, a bimetal element,means for mounting one end of said bimetal element in xed condition, anactuating member mounted on the other end of said bimetal element formovement relative to said support in response to changes of temperature,said actuating member being so disposed relative to said spring leaf asto engage said central section and move said spring leaf through saidinstable central positions when the temperature increases beyond apredetermined limit.

11. A snap switch comprising a support, a switch spring leaf, means forrigidly securing said spring leaf to said support and for pre-stressingsaid spring leaf by a longitudinal compression stress producing atendency of said spring leaf to snap from an instable central positionto one or the other of two end positions, a first contact carried bysaid spring leaf in spaced relationship to said support, a secondcontact mounted for engagement by said first contact in one of said endpositions, a bimetal element, means for mounting one end of said bimetalelement in fixed condition, an actuating member mounted on the other endof said bimetal element for movement relative to said support inresponse to changes of temperature, said actuating member being sodisposed relative to said spring leaf as to move same through saidinstable central position when the temperature increases beyond apredetermined limit, adjustable holding means constituting a seat forsaid support, and resilient means tending to keep said support seated onsaid holding means but affording freedom for said support to be liftedfrom said holding means by said actuating member through theintermediary of said spring leaf.

l2. A snap switch comprising a support, an elongated switch spring leaf,means for rigidly securing the opposite ends of said spring leaf to saidsupport and for prestressing said spring leaf by a longitudinalcompression stress producing a tendency of said spring leaf to snap froman instable central position to one or the other of two end positions, afirst contact carried by said spring leaf between its ends, a secondcontact cooperatively coordinated to said first contact,temperature-responsive means coordinated to said second contact andadapted to cause same to engage said first Contact imparting movement tothe latter and to said spring leaf through said instable centralposition, a stop, and means for movably mounting said stop and saidsecond contact for common displacement in the path of said spring leafon opposite sides thereof to limit said movement thereof.

13. A snap switch comprising a support, a bimetal strip having one endrigidly secured to said support, the other free end being movable underthe influence of a change of temperature, a switch spring leaf havingone end rigidly secured to said support and the other end rigidlysecured to the free end of said bimetal strip and being in prestressedcondition by a longitudinal compression stress producing a tendency ofsaid spring leaf to snap from an instable central position to one or theother of two end positions, a first contact carried by said spring leafbetween its ends, and a second contact mounted on said bimetal strip forengagement with said first Contact in one of said end positions.

References Cited in the file of this patent UNITED STATES PATENTS2,133,309 Schmidinger Oct. 18, 1938 2,191,670 Kuhn et al. Feb. 27, 19402,394,121 Ulanet Feb. 5, 1946 2,440,025 Singleton Apr. 20, 1948

